Diaphragm vacuum pumps may be used for various medicinal applications, in particular for drainage applications, such as wound drainage or thorax drainage. Diaphragm pumps are also well known as breastpumps for expressing human breast milk. Examples thereof include WO 96/22116, US 2009/0099511, US 2008/0287037, U.S. Pat. No. 7,094,217 and US 2008/0039781.
A drive of the vacuum pump customarily includes an electric motor which transmits rotational movement of a motor to a diaphragm via an eccentric, a connecting rod or another force transmission unit and cyclically deflects the diaphragm. A disadvantage of many pumps is that they are relatively large and loud. However, in particular in “hand-free” applications, the pump should be designed to be discrete, small, and quiet. In this context, “hands-free” means that, after being switched on, the entire device functions without hands, i.e. neither the pump nor the breast shield are held by hand.
WO 02/102437 and WO 2008/137678 show examples of “hands-free” expressing devices. The breast shield discussed is integrated in a pump housing and serves at the same time as a diaphragm for generating a negative pressure. A stepper motor may be used as the drive.